1. Field of the Invention
The present invention relates to a system and a method for recovering PTA (purified terephthalic acid) mother liquid and purifying and regenerating of catalyst, being used in manufacturing PTA; and especially relates to a system and a method wherein in the process of manufacturing PTA, the cobalt ions in the mother liquid of the PTA generated by hydrogenation reaction are adsorbed by using anion exchange resin, and the cobalt ions adsorbed by the resin are changed over to form cobalt containing inorganic acid solution by using inorganic acid, the cobalt containing inorganic acid solution thereafter is used to manufacture metallic cobalt after being processed by purifying and regenerating of catalyst, and then the metallic cobalt is used to regenerate oxidized catalysts.
2. Description of the Prior Art
A method of producing purified terephthalic acid (PTA) uses para-xylene (PX) as raw material to produce a kind of white powder of the purity of 99.95% through the reaction processes of oxidation and hydrogenation (refining). PTA is one of the main raw materials for manufacturing polyester fiber for making polyester containers (such as PET bottles), plastic for engineering and plaster.
In the process of oxidation, oxidized catalysts containing ions of cobalt, manganese and bromine are wanted and added, and cobalt and manganese ions of two valences are used as catalysts, bromine ion is used as initiating agent. In the process of hydrogenation, crude terephthalic acid (CTA) is pulped and mixed, then hydrogen is added therein to react with palladium catalyst under high temperature and high pressure, 4-carboxyl benzaldehyde (4-CBA) impurity contained therein is reduced to water soluble p-toluic acid, and is produced to form PTA after centrifugation, water washing, filtering, separating and crystal drying.
By virtue that ash contained in the crude terephthalic acid (CTA) is heavy metal ions having limited amount of 200 ppm, after centrifugation, water washing, filtering and separating, the PTA (purified terephthalic acid) mother liquid discharged contains therein about 15-25 ppm metal cobalt ions. This mother liquid of PTA containing therein metal cobalt ions is unable to be recovered for reusing in the process of manufacturing and must be discharged. Such situation will increase the burden of water treatment equipment in a subsequent stage. If the metal cobalt ions in the mother liquid of PTA can be recovered, the mother liquid of PTA can be recovered for reusing; this can largely lower the amount of water used, and an object of saving cost can be achieved.